#encoding=utf-8

import sys
import math

printf = sys.stdout.write

x1,y1,x2,y2 = map(float,raw_input().split())

X = x2 - x1
Y = y2 - y1
printf(str(math.sqrt(X**2 + Y**2))) import sys sys import math math printf = sys.stdout.write printf sys.stdout.write sys.stdout sys stdout write x1,y1,x2,y2 = map(float,raw_input().split()) x1 map(float,raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 X = x2 - x1 X x2 - x1 x2 x1 Y = y2 - y1 Y y2 - y1 y2 y1 printf(str(math.sqrt(X**2 + Y**2))) printf str(math.sqrt(X**2 + Y**2)) str math.sqrt(X**2 + Y**2) math.sqrt math sqrt X**2 + Y**2 X**2 X 2 Y**2 Y 2 x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) x2 x1,y1,x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) x1 Y = y2 - y1 y2 - y1 Y y1,x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) y1 X = x2 - x1 x2 - x1 X printf = sys.stdout.write sys.stdout.write printf y2 = map(float,raw_input().split()) map(float,raw_input().split()) y2
#encoding=utf-8

import sys
import math

printf = sys.stdout.write

x1,y1,x2,y2 = map(float,raw_input().split())

X = x2 - x1
Y = y2 - y1
printf(str(math.sqrt(X**2 + Y**2)))